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In message <4.3.2.7.0.20000725035024.0266d970@xxxxxxxxxxxxxxxxxx>, Glenn Saunde
rs writes:
>Two visual-related questions.
>
>When talking about a byte, the numbering is like this, right?
>
>128 64 32 16 8 4 2 1
yep.
>What about the bit numbering? Does it go from left to right or right to left?
Bit numbers, in order, are 7-6-5-4-3-2-1-0.
Basically, the decimal value for each bit position is 2^(bit number). The
decimal value of the byte is computed by summing 2^(bit number) for all
the bits whose value is "1".
>So when drawing player sprites for use in memory by using graph paper, what
>you see is what you get on the screen if you feed it numbers like the
>above, ala:
>
>X X X X X X X X = 255
>X 0 0 0 0 0 0 0 = 128
>X 0 0 0 0 0 X 0 = 130
Yes, but can you use the numeral "1" instead of "X" to represent true?
An "X" typically means don't know, or don't care.
>Also, how I'm going to explain VDEL is that it has the net effect of
This is good. You just explained VDEL to me...congrats! (and thanks! :)
>Also, I've noticed that a lot of source code stores sprite data upside
>down. Any reason why? Do they scan memory by decrementing a counter or
>something?
Yes, it's much easier to detect a zero than it is to detect a byte overflow,
because of the zero flag.
-Chris
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